Updating the SNDERR line to output the hex value of equal->klass->PortDescriptors[index] on errors showed it had a value of 0x15 which is LADSPA_HINT_LOGARITHMIC | LADSPA_PORT_INPUT | LADSPA_PORT_CONTROL, which triggers the error. Altering that line to be:

Updating the SNDERR line to output the hex value of equal->klass->PortDescriptors[index] on errors showed it had a value of 0x15 which is LADSPA_HINT_LOGARITHMIC | LADSPA_PORT_INPUT | LADSPA_PORT_CONTROL, which triggers the error.

Its actually a change in media-plugins/caps-plugins which added another value: